1. Field of the Invention
The present invention relates to an image recorder for emitting photo-beams onto an objective surface to record an image on the objective surface, and more particularly, it relates to an improvement in an optical fiber array unit adapted to the image recorder.
2. Description of the Background Art
An optical fiber array having a bundle of optical fibers is used in an image recorder for high density image-recording. The fiber array is advantageous in that the spatial intervals of light emission points are reduced to the diameter of, each fiber, i.e., 0.125 mm to 1.0 mm. However, the clads in respective fiber ends do not contribute light emission and blank areas corresponding to the clads appear on the recorded image, so that the density of scanning lines is reduced on an image-recording medium.
U.S. Pat. No. 4,991,930 discloses an improved fiber array as illustrated in FIG. 9A. A plurality of fiber rows 901-903 are stacked into a staggered arrangement with an alternate half-pitch deviations to increase the recording density.
U.S. Pat. No. 5,321,426 discloses an inclined arrangement of a single fiber row as illustrated in FIG. 9B to prevent the undesirable blanks between scanning lines.
In the former prior art, U.S. Pat. No. 4,991,930, the position of the first fiber row 901 is fixed by V-shaped grooves while respective fiber positions of the second fiber row 902 are fixed between the fibers of the first fiber array 902. The half-pitch deviations between the first and second rows 901, 902 contributes the improvement of the recording density. However, the third row 903 is aligned just above the first row 901 and the recording density is not further increased by the third row 903. The improvement of the recording density is limited to twice the conventional one.
On the other hand, the arrangement of the latter prior art, U.S. Pat. No. 5,321,426 is effective to further increase the recording density. However, a wide array of fibers is required to further improve the recording density because the fiber array is sinble and linear. The wide array of the fibers increases an imaging field and it requires a lens system having large aperture, which causes a problem of aberration. Further, when the photo-beams are emitted onto a recording medium wound around a rotary drum, the focal points of respective photo-spots are hardly coincident with the curved surface of the recording medium, since the distances from the respective fiber ends to the curved surface of the recording medium are not substantially constant between the center part and both end parts of the wide fiber array.
The present invention is directed to an image recorder for scanning an objective surface with a plurality of photo-beams in main scanning direction and a subscanning direction to record an image on the objective surface.
According to the present invention, the image recorder comprises: a light source for generating light; an optical fiber array unit comprising a plurality of optical fibers arranged into a plurality of optical fiber rows for receiving the light and emitting a plurality of photo-beams, and at least one spacer substrate inserted between the plurality of the optical fiber rows, the spacer substrate having top holding means, formed on a top surface thereof, for holding ones of the optical fiber rows and bottom holding means, formed on a bottom surface thereof, for holding other ones of the optical fiber rows; and an optical system for transmitting the plurality of photo-beams from the optical fiber array unit onto the objective surface.
The top holding means is formed in parallel with the bottom holding means, and both the holding means are staggered in the subscanning direction.
In an aspect of the present invention, a plurality of spacer substrates are provided in the optical fiber array unit, and the plurality of spacer substrates are stacked such that the holding means of one spacer substrate fits in with the bottom holding means of another spacer substrate.
In a preferred embodiment of the present invention, the plurality of optical fiber rows are staggered in the subscanning direction by integer times of the amount P/N, where P is a fiber arrangement pitch of in each optical fiber row, and N is the number of optical fiber rows included in the optical fiber array unit.
Preferably, the optical fiber array unit further comprises a first cover substrate provided above a top spacer substrate among the plurality of the spacer substrates and having holding means fitting in with the top holding means of the top spacer substrate, and a second cover substrate provided below a bottom spacer substrate among the plurality of the spacer substrates and having holding means fitting in with the bottom holding means of the bottom spacer substrate.
Only one fiber row may be held in each tunnel space, or two rows may be held in each tunnel space.
In a preferred embodiment of the present invention, the top and bottom holding means comprise a plurality of grooves arranged in the subscanning direction.
In another aspect of the present invention, an image recorder comprises a light generator for generating a plurality of lights modulated by image signals; a plurality of flexible linear optical guides for transmitting the plurality of lights to an objective surface and having each light-emitting end arranged on a staggered matrix without positional overlapping of the light-emitting end in a row direction; and at least one spacer inserted between any row of the staggered matrix.
The present invention also provide a fiber array unit usable in the image recorder.
Accordingly, an object of the present invention is to increase a recording density to attain a fine image recording without increasing an imaging field of photo-beams emitted form an optical fiber array unit.
Another object of the present invention is to obtain a rigid structure of an optical fiber array unit in which respective fiber are well-positioned.
Further another object of the present invention is to obtain a rigid structure of an optical fiber array unit in which respective fiber are well-positioned.
Further another object of the present invention is to attain a fine image recording without increasing costs.